There are numerous processes in which the particle size of materials, such as paste or dough-like masses, semi-liquids etc., is reduced by passing the material through a gap or nip between rollers. As an example, in a chocolate making process, the ingredients of the chocolate mass are mixed and the particle size of the mixture is thereafter reduced in a so-called pre-refiner. The particle size is then further reduced in one or more refiners and subsequently the mass is supplied to one or more devices for conching or homogenize same. The described pre-refiner, which serves to reduce the particle size and adjust consistency of the chocolate mass, may comprise rollers defining a gap or nip between them, through which the chocolate mass is passed to reduce the particle size.
In this context, EP 0 123 015 A2 describes a device for monitoring and controlling the thickness of a chocolate mass, in which colorimetric signals are measured and used to control the pressure applied between the rollers.
EP 0 953 291 B1 describes a method for refining a confectionery material, such as a chocolate mass, in which the distance between rollers is continuously measured, compared with a reference distance and used to adjust the revolution speed of one of the rollers.
Finally, U.S. Pat. No. 6,182,914 B1 teaches how to measure the force exerted by a confectionery material on rollers and how to adjust the nip between the rollers so as to match a target force.